Brazos Estuary Instream Flow Water Quality and Nekton Study

Purpose/Objectives

The primary objectives of this project are to 1) characterize the flow regime, tidal
dynamics, and water quality; and 2) quantify species composition, distribution, and
density of larval, juvenile, and adult nekton that utilize the Brazos River Estuary.

Study Area

Lower Brazos River, Brazoria County, Texas

Project Period

2016 – 2017

Description

The state of Texas is currently in the process of validating environmental flow recommendations
in an effort to maintain sound ecological environments in rivers and estuaries. It
is assumed that the primary mechanism regulating production in estuaries is the discharge
of freshwater, which creates an optimal salinity gradient. Within a riverine system,
this salinity gradient operates on a dynamic linear scale influenced by freshwater
inflow and tidal forces.

Expanding on previous research conducted by EIH in the Brazos River Estuary near Freeport in 2012 and 2014, field sampling of flow
regimes and biological monitoring were resumed in the fall of 2016. Collections to
characterize instream flows include water quality, physical parameters, and biota.
Five sites have been selected in the tidal portion of the lower Brazos River from
the mouth to 42 river-kilometers upstream. Water quality profiles, as well as continuous
monitoring, will be conducted to characterize typical water quality parameters along
a longitudinal gradient from fresh to saltwater. Nekton collections using otter trawls,
beam trawls, and plankton nets are being assessed.